The present invention relates generally to tone synthesis apparatus and methods for synthesizing tones, voices or other desired sounds on the basis of waveform sample data stored in a waveform memory or the like. More particularly, the present invention relates to a tone synthesis apparatus and method for synthesizing a waveform of a sustain portion of a tone, where generation of the tone lasts in a relatively stable manner, while variably controlling a waveform-switching time (so-called “crossfade time period”).
There have been known tone synthesis apparatus which can synthesize a vibrato rendition style waveform with a high quality for a plurality of vibrato cycles. For that purpose, the tone synthesis apparatus discretely extract a plurality of waveforms (i.e., partial waveforms) from vibrato-modulated (pitch-modulated) continuous waveforms of one vibrato cycle range sampled on the basis of actual performances of natural musical instruments, and stores the thus-extracted waveforms as template waveforms. In reproduction of a tone, the tone synthesis apparatus repetitively read out the stored template waveforms while switching between the template waveforms in accordance with a predetermined sequence, to thereby synthesize a high-quality vibrato rendition style waveform for a plurality of vibrato cycles. One example of such tone synthesis apparatus is disclosed in Japanese Patent Publication No. 3669177 corresponding to U.S. Pat. No. 6,150,598. The tone synthesis apparatus disclosed in the No. 3669177 patent publication is arranged so that, when switching is to be effected between template waveforms, the adjoining template waveforms are subjected to crossfade synthesis for a predetermined waveform switching time (so-called “crossfade time period”).
However, the conventionally-known tone synthesis apparatus permitting high-quality tone synthesis, like the one disclosed in the No. 3669177 patent publication, are arranged to only read out the template waveforms in accordance with the predetermined sequence; namely, the conventionally-known tone synthesis apparatus are not arranged to change characteristics of the tone as desired in accordance with dynamics information (tone volume level information), pitch bend information (pitch modulation information), etc. input as needed during synthesis of the tone. Further, in the conventionally-known tone synthesis apparatus, the above-mentioned crossfade time period, over which crossfade synthesis is to be performed, is empirically set at a predetermined reference time (e.g., 50 ms (milliseconds)) as a balanced crossfade time well reflecting a tone color variation, and thus, a crossfade time period optimal to each individual waveform switching can not be set in accordance with information triggering tone-color-change-involving waveform switching, such as dynamics information and pitch bend information input as needed during tone synthesis. Thus, if there has occurred a sudden variation in the input dynamics value, such as in a change from “sforzando” to “piano”, the waveform switching would be undesirably delayed. Namely, the tone color variation may not sufficiently follow the input dynamics value variation, which is very disadvantageous. Conversely, if the input dynamics value has varied slowly, the waveform switching would be completed earlier than initially intended, so that there would arise a stepwise tone color variation in a portion in question. Such a stepwise tone color variation would catch user's attention and tends to be offensive to the ear of the user.